New form of solid carbon exhibits diverse range of properties

Researchers from North Carolina State University have discovered a third form of solid carbon that is distinct from graphite and diamond.

The new form, or phase, has been named Q-carbon and it has a range of surprising properties, such as being ferromagnetic, harder than diamond, and glowing in the dark when exposed to low energy. Other forms of solid carbon are non-magnetic.

A scanning electron microscopy image of microdiamonds made using the new technique.

“We’ve now created a third solid phase of carbon,” said Jay Narayan, a professor of materials science and engineering at NC State and lead author of three papers describing the work. “The only place it may be found in the natural world would be possibly in the core of some planets.”

Q-carbon is produced by starting with a substrate such as sapphire, glass or a plastic polymer. This is then coated with elemental carbon that does not have a well-defined crystalline structure like graphite or diamond. The carbon is hit with a single laser pulse lasting around 200 nanoseconds, raising its temperature to about 4,000 Kelvin. After cooling rapidly, a thin film of Q-carbon is left. Films can be made to thicknesses between 20 and 500 nanometres.

The researchers have also developed a patented method to create diamond-like structures from Q-carbon at room temperature and ambient atmospheric pressure. This is done by tweaking the rate of cooling through using different substrates and varying the length of laser bursts. Narayan believes the process could lead to inexpensive Q-carbon materials replacing diamond in a range of industrial, medical and electronic applications.

“We can make Q-carbon films, and we’re learning its properties, but we are still in the early stages of understanding how to manipulate it,” he said. “We know a lot about diamond, so we can make diamond nanodots. We don’t yet know how to make Q-carbon nanodots or microneedles. That’s something we’re working on.”